In general, useful physiologically active substances having an asymmetric structure are frequently specific antipodes and the tendency is remarkable in the fields of medicaments, agricultural chemicals, food additives, etc. For example, (1R, 2S, 5R)-5-methyl-2-(1-methylethyl)cyclohexyl alcohol (hereinafter, is referred to as "l-menthol") has a strong peppermint smell with a cool feeling activity and is used as a flavor but it is known that d-menthol which is an optical antipode is poor in a refreshing feeling and has a sweet flavor a little [Motoichi Indo, Koryo no Jissai Chishiki (Actual Knowledge of Perfume), page 79, published by Toyo Keizai Sinpo Sha, 1975].
On the other hand, U.S. Pat. No. 4,459,425 discloses 3-{(1R, 2S, 5R)-[5-methyl-2-(1-methylethyl)oxy-1,2-propanediol (the compound is also called "3-l-menthoxypropane-1,2-diol").
According to the description of the U.S. patent described above, 3-l-menthoxypropane-1,2-diol is obtained by forming the sodium salt of l-menthol with metallic sodium or sodium hydride, reacting the sodium salt with allyl halide to provide 3-l-menthoxypropan-1-ene, oxidizing the product using an organic peracid to form an oxide, and then hydrolyzing the oxide.
Also, according to the description of the foregoing U.S. patent, since 3-l-menthoxypropane-1,2-diol has a property of giving a cool-feeling activity but does not have a smell different from l-menthol, for the purpose of imparting a cool-feeling activity to an article without giving any influence to the flavor of the article by utilizing the foregoing property, the compound is compounded with compositions for oral cavity such as a tooth powder, a wet tooth powder, a tooth paste, a chewing gum, etc., or food and drink such as a sherbet, a hard candy, etc.
Furthermore, it is proposed to compound the foregoing compound with cosmetics such as cosmetic materials as described in JP-A-60-25908 and JP-A-63-208505 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), eye pack agents as described in JP-A-62-96403, hair cosmetic materials as described in JP-A-62-192312, etc., and also with aerosol compositions for anti-inflammatory analgesic agents as described in JP-A-63-264522, etc.
However, the 3-l-menthoxypropane-1,2-diols disclosed in the specifications of the foregoing patent applications are compounds wherein the asymmetric center at the 2-position of the propanediol in molecule is uncertain. In the production process described in U.S. Pat. No. 4,459,425 described above, three asymmetric centers in the l-menthol structure of the four asymmetric centers in the molecule of 3-l-menthoxypropane-1,2-diol are confirmed but no steric control of the 2-position of the propanediol is made and a racemic modification only, which is an equivalent mixture of the (2S) isomer and the (2R) isomer, can be synthesized.
There are no examples that the (2R) isomer of 3-l-menthoxypropane-1,2-diol is isolated from the (2S) isomer thereof and that they are synthesized and properties of them are compared and confirmed, and also there are no reports about various compositions containing them.